The best thing to do, I think... is to try see things through the other person's eyes. Try imagine oneself being in his or her position or situation. Just because you think you know what to do for or what to tell that person... doesn't mean that you're right. You need to look further than to what is visible. Both mind and heart need to be a part of this.
We can't read the mind of others... but we can communicate in such a way that we get to know at least much more, about how this person is feeling and what his or her needs are. Our ears are very important! Not only to hear with- but to really LISTEN.

Nobody's perfect... We all fail in doing the correct thing... But trying to see things from another person's point of view, is a good start.

Another part of this is to be willing to forgive others. If I've done something wrong and I'm feeling sorry about that, apologizing to the person in question... I would be happy to be forgiven. So... if someone's making me sad by doing something to me... I should forgive too.

By writing "you" in this post... I don't mean that I don't need to think about this too! I'm faaaar from perfect! I should have written "we" instead of "you"... like LMo did.

Learning by doing! If we put our minds and hearts to it... and try to do our best to be good to others... then we'll grow in that knowledge as time goes by.